1. Technical Field
The present invention relates to data management methods; particularly, it relates to data management methods wherein digital content is encrypted with special access information and distributed.
2. Description of Related Art
Electronic data in computer program software and electronic publishing materials is vended stored on magneto-optical disks (MO), digital video disks (DVD), floppy disks (FD), mini disks (MD) and other recording media. Electronic data thus is generally easy to copy, and illicit copies are frequently made. That copyrights on the software vendor and publisher end will be infringed and considerably hinder profits is therefore a worry.
The situation is the same with electronic data containing still image data and motion picture data distributed via the Internet, CATV and other networks: illicit copies are made frequently, consequently damaging copyright holders' profits.
For protecting so-called digital content, such as electronic data stored on the recording media described above and electronic data distributed via the variety of networks, it has been the practice to encrypt the digital content using an encryption key, and the thus distributing the substantive data that has been encrypted.
Assuming, for example, that a user accesses a content distributor from his or her own personal computer, then downloads the digital content onto a hard disk, and thus uses the digital content: To start with, the user accesses a host computer and obtains a plug-in module for downloading. Thereafter, the user forwards, to the host computer, an in-use hard disk drive identification number, an in-use computer CPU identification number, and other identification information items unique to the user.
On the content distributor end, substantive data in which digital content is encrypted with a content key and authorization information in which the content key is encrypted with user-specific identification information, is sent to the user end.
On the user end, the encrypted substantive data that has been sent and the authorization information are recorded as is encrypted on the hard disk. When using the digital content, employing user-specific identification information such as the hard disk drive identification number, the authorization information is decrypted and the content key is thereby obtained. The digital content is decrypted with the content key and thus used.
Herein, when granting individual users the right to use the digital content, the encryption key for encrypting the digital content can be made common, and use privileges can be granted individually to users by encrypting a decryption key utilizing user-specific information different for every user.
Wherein data is distributed by the methods described above, the data distributor is required to forward separately the encrypted digital content and the authorization information serving as the decryption key for the encrypted digital content.
Further, on the user end, the encrypted digital content and the authorization information that have been forwarded have to be stored separately on the recording medium.
Consequently, if the authorization information is damaged during the course of being forwarded to the user end from the data distributor end, or if the authorization information is otherwise damaged or lost due to some mishap on the recording medium on the user end, the digital content will become unusable. This makes it necessary to go through a process for acquiring second-time authorization information.